Turbocharger: Description and Operation

PURPOSE
Systems which increase the amount of air sent to the engine are either turbocharging type (using exhaust gas to turn the turbine) or supercharging type (using the engine crankshaft etc. to mechanically turn the pump). This engine uses the turbocharging type.

OPERATION

Schematic View Of Turbocharger System Connections:

The Two-Way Twin Turbo System uses 2 turbochargers. Under this system, the 2 compact turbochargers provide separate functions according to the engine running conditions. While 1 turbocharger gives boost at low rpm and low engine load conditions, the 2 turbochargers together give boost at high rpm and high engine load conditions.

Low Engine Speed
Since the intake air control valve and exhaust gas control valve are closed during low engine rpm operation, the waste gate valve is also closed. Therefore, only the No. 1 turbocharger will provide the boost pressure.

Turbocharger Sequential Operation
When the charging pressure reaches a predetermined level, the exhaust bypass valve opens progressively to supply the exhaust gas to the No. 2 turbocharger causing the No. 2 turbocharger turbine wheel to start rotating. Accordingly, this process smooths out the joining of the boost pressure from the No. 2 turbocharger when it starts boosting.

High Engine Speed
The exhaust gas control valve and intake air control valve are open, allowing the No. 1 and No. 2 turbochargers to boost. At this time, even if the exhaust bypass valve operates, it cannot effect any boost pressure control, since it is located downstream of the No. 2 turbocharger. During a high speed operation, it is the waste gate valve that executes the boost pressure control of the entire system, in place of the exhaust bypass valve.